The East End Thrift Store will be hosting a giant vintage jumble sale this weekend (19-20 September 2009).
You can have a good rummage and fill up a bag for £10 or £20.
I have never been to their store but I have heard mixed things about this place: some people say the staff are pretentious and others can't get enough of it. I couldn't give a rats ass if their customer service is pony, as long as I can get some good stuff for peanuts I will be pleased.
Watermans Building Society